package com.zcah.system.shiro;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;

import com.zcah.common.util.JsonUtils;
import com.zcah.common.vo.R;

/**
 * 请求流程 preHandle->isAccessAllowed->isLoginAttempt->executeLogin
 * @author ke
 *
 */
public class JWTFilter extends BasicHttpAuthenticationFilter {

	private static final Logger LOGGER = LoggerFactory.getLogger(JWTFilter.class);

	/**
	 * 判断用户是否想要登入。 检测header里面是否包含Authorization字段即可
	 */
	@Override
	protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
		HttpServletRequest req = (HttpServletRequest) request;
		String authorization = req.getHeader("Authorization");
		return authorization != null;
	}

	@Override
	protected boolean executeLogin(ServletRequest request, ServletResponse response) throws Exception {
		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		String authorization = httpServletRequest.getHeader("Authorization");

		JWTToken token = new JWTToken(authorization);
		// 提交给realm进行登入，如果错误他会抛出异常并被捕获
		getSubject(request, response).login(token);
		// 如果没有抛出异常则代表登入成功，返回true
		return true;
	}

	/**
	 * 对跨域提供支持
	 */
	@Override
	protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		HttpServletResponse httpServletResponse = (HttpServletResponse) response;
		httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
		httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
		httpServletResponse.setHeader("Access-Control-Allow-Headers",
				httpServletRequest.getHeader("Access-Control-Request-Headers"));
		// 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
		if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
			httpServletResponse.setStatus(HttpStatus.OK.value());
			return false;
		}
		return super.preHandle(request, response);
	}
	
	/**
	 * 通过注解去限制用户权限
	 */
    @Override
    protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
        if (isLoginAttempt(request, response)) {
            try {
                executeLogin(request, response);
            } catch (Exception e) {
                response401(response);
            }
        }
        return true;
    }

	/**
	 * 未授权401处理
	 */
	private void response401(ServletResponse resp) {
		PrintWriter out = null;
		try {
			HttpServletResponse httpServletResponse = (HttpServletResponse) resp;
			httpServletResponse.setCharacterEncoding("utf-8");
			httpServletResponse.setContentType("application/json; charset=utf-8");
			httpServletResponse.setStatus(401);

			out = httpServletResponse.getWriter();
			out.write(JsonUtils.toString(R.error(401, "未认证请求")));
			out.flush();
		} catch (IOException e) {
			LOGGER.error(e.getMessage());
		} finally {
			if (out != null) {
				out.close();
			}
		}
	}
}
